I hope everyone is patient. I have been saving coins for a few years and now am retired. I have quite a few coins with questions. I know from research that this coin is usually found in proof sets,but looking at all my 1990s this one looked totally different.Could this be the 1990 no s coin?

Normal buisness strike so no mint mark would be present as it's from Philadelphia. A proof would have mirrored field and frosted reliefs with a squared edge.

No mint mark simply means it was minted at the Philadelphia mint, rather than the Denver or San Francisco mint. You have a well struck business strike cent made of zinc with a very thin layer of copper over it. We sometimes refer to these a "Zincolns" and because of the metal change in late 1982, many, me included, consider them crap. Good hunting.

It's not the proof. Look up the proof with the S and see the difference in those. The No-S proof looks the same as the proof minus the S.